Flame-resistant mineral fiber tile



April 26, 1966 J CADQTTE ET AL 3,248,257

FLAME-RESISTANT MINERAL FIBER TILE Filed 001;. 24. 1960 In vez zzors United States Patent C) 3,248,257 FLAME-RESISTANT MINERAL FIBER TILE John E. Cadotte and Edward W. Juntti, Cloquet, Minn, assignors to Woods Conversion Company, St. Paul, Minn,- a corporation of Delaware Filed Oct. 24, 1960, Ser. No. 64,622 13 Claims. (Cl. l17126) The present invention relates to mineral fiber ceiling tile panels, particularly adapted to remain in mounted position and there to function as fire-stops.

Mineral fiber tile, such as squares and other forms of panel, commonly'contain a small percentage of combustible content, for example, vegetable fibers for imparting certain physical properties, and organic binder, such as resin or starch, to hold the fibers in bonded relation at a density in the range from l2-to 75 pounds per cu. ft. The combustible content can be regulated so that on exposure of the body to a very hot flame, such as at 2,000 F., the organic content is burned away, and the mineral content remains in panel form without disintegrating or crumbling, although there is shrinkage in the lanar direction of the tile. However, there is a resulting sagging of the panel when mounted at opposite edges, when the panel lacks some special processing in manufacture or some special treatment after manufacture tending to stabilize the tile and to oppose the tendency to sag.

The present invention relates to such processing and treatment, and it is, therefore, an object of the invention to provide a mineral fiber tile which may be suspended from opposite edges in a manner to provide a satisfactory fire-stop when exposed to the flames of a configuration within the quarters for which the tile provides a ceiling.

Such ceilings commonly'have a plenum chamber above the tile. By preventing the tile from dropping, i.e., by minimizing its deformation when exposed to flame, the ceiling continues to provide a fire-stop limiting temperature rise in the plenum chamber, thereby protecting the building structure beyond the plenum chamber from contact by the flame.

So-called fire-retardant and fire-resistant tiles have such properties in varying degrees. Governmental and insurance regulations cutomarily set standards to be met commercially, and specify test procedures, so that tiles are rated according to their response to a test, for example, according to the lengths of time which they remain in place.

The present invention involves the application of fibercoating material to mineral fibers of a mineral fiber tile, to oppose the tendency of the tile to deform on exposure to flame. In the preferred manner of carrying out the invention, the resulting tile or panel meets a certain test permitting use of the tile when meeting one or more tests I is a prerequisite to use.

The invention involves the use of liquid containing chemical means, preferably aqueous suspensions, or solutions, or both, to be applied to the mineral fibers and to provide dry material on the surfaces of dry fibers which is a refractory deposit on the fiber surfaces, thus to stiffen them and to resist the normal tendency to flex when highly heated. The material to be applied may be so incorporated that fibers throughout the body are so coated with refractory material, but this method with some materials olfers difliculties. When a slurry is dewatered which contains the fibers and certain kinds of treating agents which are in solution or present as dispersions in water, some of the agent is lost in the removed water. Economy in use of that type of processing material is achieved by applying the liquid containing it to the surface of a fiber felt after dewatering, either while still wet from pressing a dewatered felt, or dried, or in two applications, one on 3,248,257 Patented Apr; 26, 1966 the wet pressed felt and another after drying. When the felt is formed by an air-laying process, that type of treating agent may be introduced to the body of the fibers without such loss. Certain other materials which are applied and which react after application to produce a water-insoluble agent, are not so lost in dewatering.

When the refractory-forming agent is present throughout the body of the fiber felt, various methods of mounting the tile are available. But, when the processing is limited to the back face of a mounted tile, the method of mounting the tile is limited.

Mineral tile or panel is commonly mounted at opposite edges by suspension from metal runners in such a way that the metal is hidden from view and protected from exposure to flame by a flange portion of the tile. The metal is more sensitive to heat than the mineral fiber body, and one objective in mounting is to protect the metal from exposure to direct heat of a flame. When the edge-mounted mineral body sags to an excessive extent, it may expose the metal runners to flame or direct heat of a flame, according to the design of the joint, which runners then warp or bend, resultingly permitting the body to drop or to be dislocated so that an opening in the tile ceiling is produced. Although a tile may remain integral on long exposure to heat or flame, it is the mounting of it that also must resist the heat and flame so that the tile remains mounted and its mounting means withstands the heat sufficiently to prevent dropping of the tile and prevent formation of an opening through the tile ceiling.

With respect to mineral fiber tile horizontally mounted as herein illustrated and described, it has been found that I when it lacks a treatment according to the present invention, its shrunken form will bend or sag downwardly when heated to redness to an excessive extent, and thus so shorten its span between metal runners that the metal could be exposed. Sometimes, the shortening pulls it away from at least one supporting metal flange, letting the tile drop. If this does not take place-the exposed metal runner so softens and warps that it permits the tile to droop without dropping, or to drop, in either case providing an opening through the tile-ceiling for access of flame to the space above the tile.

By applying a liquid composition containing soluble or dispersed chemical means in a manner to coat the mineral fibers at appropriate locations in the tile, the normal tendency of the tile to deform when exposed to flame is decreased. The amount to be used and the manner and place of applying it predetermines the extent to which the tendency to deform is minimized. Also, the composition of the tile itself and its density are influencing factors, making it a matter of empirical experimentation for a particular composition of file, to determine how much of the chemical means is required for any selected method of application, to meet some specified test. It is, therefore, to be understood that the invention broadly contemplates the application of chemical means to fibers of a mineral fiber tile, without limiting the invention to meet any particular test, or to provide any particular degree of the desired effect.

The invention is illustrated by reference to one set of conditions, including tile composition, method of mounting and a prescribed test, and with variations in the method of application.

FIG. 1 is a view of a suspended tile ceiling looking at the back faces of tile squares mounted on parallel metal runners.

FIG. 2'is an enlarged broken edge View of a tile taken on line 22 of FIG. 1.

FIG. 3 is a view showing the tile of FIG. 2 joined with two similar tiles, all mounted on parallel metal runners shown in cross-section on the line 22 of FIG. 1.

FIG. 4 is a view of one of the joints of FIG. 3 showing the manner in which the tiles pull away from the runners as a result of sagging.

FIG. 5 is an enlarged fragmentary view of a tile partly in cross-section, wherein the stippling indicates the presence of sodium aluminate.

In the drawings, the tiles are illustrated by conventional 12-inch squares, without intent to limit the shape or size to the illustrated for-m. However, the invention applies to larger tiles, such as 2 X 4 feet similarly mounted. Suspended ceilings of such tile commonly have a plenum chamber above them and under a floor or roof above the tile in which space service equipment may be housed. The tile ceiling should confine flames to the space below it, at least for some predetermined required period of time. In FIG. 1, the numerals designate parallel metal runners to which the tiles are mounted in a manner to protect the runners by at least a portion of the thickness of the tile. The runners 10 are suspended by means not shown which form no partof the present invention.

One way to mount the tile to the runners 10 is to provide the runner with two lower flanges 11 and 12, in a T-formation with a vertical web 13, and to provide kerfs or grooves in side edges of tile to receive flanges.

The tiles have interfitting tongue and groove structures in the two pairs of opposite edges, and these are constructed to provide continued protection to the metal flanges. A joint may open by limited sagging of tiles. I

In FIG. 1, a tile 15 is indicated as having a tongue 16 entering a groove in like adjacent tile 17, which groove duplicates groove 18 in tile 15, said groove 18 receiving a tongue of tile 19. The remaning tongue and groove of tile 15 for mounting on the runners 10 are shown in FIGS. 2 and 3.

A tongue 20 extends to the right in FIG. 2, being about /3 as thick as the tile which is approximately %-inch thick. The upper face 21 of the tongue extends into the body of the tile as a kerf 22, which kerf receives a flange 11 of a runner 10. The tile edge-face 23 above the tongue 20 is inwardly of the tile edge-face 24 below the tongue 20.

The opposite grooved edge of tile 15 has a groove 26 in the central third of its thickness to receive a tongue 20 of another tile, thus forming two encompassing flanges 27 and 28.

FIG. 3 shows tile 15 suspended on runners 10 alongside two similar tiles 15 and 15 of which the parts corresponding to the parts in tile 15 are similarly designated. In this relation tile flange 27 rests on runner flange 12 and forms a space 30 between it and the end of the opposite flange 23 for the web 13 of runner 10. The runner flange 11 fits into kerf 22.

FIG. 4 shows the normal joint of FIG. 3 opened up to a degree, which happens when the tiles sag. In the normal joint the runner flanges 11 and 12 are protected by about two-thirds of the thickness of the tiles. As the joint opens, the extreme edge portion of runner flange 12 loses some of this protection from the heat and flame which has caused the tiles to sag. The extent to which the joint may open before exposing the runner or dropping a tile is controlled by designing dimensions. To lengthen the tongue and groove to protect the runner results in weakening the tile at the joint and in likelihood of damage to a tile unit in handling.

The present invention limits the opening of a joint during exposure to flame by minimizing the tendency of a tile to deform and thus prevent that degree of deformation which could drop the tile or open a joint.

It has been found that when only the fibers at the back face and in the layer adjacent the back face have on their surfaces deposits of chemical means Which is or which forms a refractory material, the treated fibers in their assembled relation in the tile form a rigidifying backing for the tile which stiffens it and lessens the degree of deformation. When the tile is mounted in the manner shown and when the chemical means is present only at the surface fibers, the entire back must be treated including especially the regions of the tile flanges which overlie the runner flanges 11 and 12. Otherwise, the tile flanges'ltend early to break and let the tile drop.

A variety of chemical means is available for selection to provide, when heated, refractory coverings on the fibers. Phoephate salts are suitable, such as sodium tripolyphosphate, and other chemical means, such as sodium chloride, sodium sulfate, ferric sulfate, ferric chloride, zinc hydroxide, zinc chloride, zinc oxychloride, mixtures of zinc chloride and zinc oxychloride, aluminum sulfate, sodium silicates, calcium aluminate, sodium aluminate, and magnesium sulfate.

However, the character of the mineral fiber is important when selecting the chemical means for the processing of the present invention. When the fibers are reactive, as when they are alkaline, or contain sulfides, as does mineral fiber made from slag, the refractory material can be formed as a result of reaction of the ap' plied chemical means with the fiber. Glass fibers are much less reactive to the chemical means, and in fact, practically inert in the process of producing the treated tile. To what extent there may be reaction at red heat is not material to this description.

Thus, when ferric chloride in solution is applied to slag wool fiber, hydrogen sulfide is released and red ferric hydroxide is deposited on the fibers. Aluminum sulfate likewise-liberates hydrogen sulfide, and forms aluminum hydroxide.

When zinc chloride is used, it is more effective when up to one-half mole of caustic soda per mole of zinc chloride is used with it, thus forming zinc oxychloride (ZnOHCl) in whole or in part. Because of the reaction to form zinc oxychloride, a mixture of zinc chloride and of caustic soda is the preferred chemical means for addition to the slurry. The resulting zinc oxychloride adheres to the fibers and is not lost when felting on a Fourdrinier machine. A small amount of a coagulant such as polycrylamide assists the coating of the fibers by the zinc oxychloride by flocculation.

Sodium aluminate is the preferred agent for surface treatment, being alakline and, therefore non-reactive with glass fibers and slag wool. In practice, the preferred tile board is made to include the zinc oxychloride and the finished board is treated to back the tile with sodium aluminate.

Even though the mineral content of the fibers is characterized by a melting point below a red heat at which an untreated tile sags, the fibers do not melt, and they retain a felted relation holding the tile body together even though the organic content has burned away. Fibers not having a refractory coat thereon which have been examined after cooling from a red heat, appear to have shrunk but remain loosely held together as originally felted. The fibers which before the heating were processed to have a refractory deposit thereon exhibit less shrinkage and exhibit the coating material variously covering or spotted over the surfaces of fibers.

The reason why these material function is not precisely known, but the belief is presented that because of the refractory character of its residue it rigidifies and isolates the surfaces of individual fibers on which it lies, and thus inhibits shrinkage and flexure of the fiber when softened by the intense heat, and it holds the coated fibers more closely to their original relative positions.

The mineral fiber tile is one formed at a thermal insulating density suitable for adequate strength for the tile for commercial handling and for sustaining itself when mounted at its edges. The mineral fibers may be glass fibers or the various forms of mineral wool or slag wool. A suitable tile is made by felting an aqueous slurry of a slag wool, cellulosic fibers, asbestos fibers and starch grains, on a Fourdrinier machine, draining water from the mat, pressing to a density for drying to aboard of 12 to 30 pounds per cu. ft., heating the pressed wet mat throughout to a temperature effecting gelatinization of the starch grains before drying the mat, and then drying the mat with the gelatinized starch providing the bond. Such a board may be treated according to this invention after being so made. ticed by introducing the treating chemical into the process at numerous stages before the final drying. The density to which the board is formed is related to the size of tile units to be made. For tile 12 x 12 x /6 inches a density in the range from 22 to 25 pounds per cu. ft., is preferred.

Suitable formulations for handleable fire-retardant minenal board having density in the range from 12 to 75 pounds per cu. it, are given in Tables I and II.

Wax-size suspension (aqueous).

*As disclosed in Olson U.S. Patent No. 2,754,206.

For forming the preferred board with inclusion of chemical means for the present invention, the composition of Table III may be used.

Table III Parts by weight Slag wool fibers 79.1 Amosite fibers 2.6 Sulfite cellulose fibers 2.0 Starch grains 13.5 Wax-size suspensions 0.8 Zinc chloride 3.3 Caustic soda 0.5 Coagulating agent 0.0175

A board of 23 /2 pounds per cu. ft. is formed as described. Then, the dry board in the form of cut tile units is coated over the entire back of the tile with sodium aluminate composition of Table IV,.at the usage of 17 pounds of solids per M sq. ft.

Sodium aluminate has been found so far to be the most effective material for application to the back of a mineral fiber tile. It melts at 1650 C. or 3000 R, which is well above the temperature to which the back of the tile is exposed. It is soluble in water to a limited extent. There are numerous ways to locate sodium aluminate throughout the tile or at and adjacent the back face of the tile. It may be applied as such, or may be formed in situ. It may be sifted into the surface as a powder, or applied as a paste or suspension, either aqueous or nonaqueous. It is preferably used in an aqueous solution containing an excess of undissolved finely divided sodium aluminate. Confinement at and adjacent the back face is sufficient and preferred, thus permitting the exposed face to be decorated, for example. When the tiles are mounted in the manner shown in the drawing, it is necessary that the location of the sodium aluminate be such as to lie in or on the flanges 23 and 27 to strengthen them for holding during exposure of the tile to flame. Penetration of the aqueous composition is minimized by the Also, the invention may be pracpresence of undissolved particles and a thickening agent, such as methyl cellulose, starch paste or the like. The thickening agent functions additionally to keep the undissolved content of sodium aluminate in suspension. Various methods of application require viscosity control for particular apparatus, or operation, or panel material, and varying the thickening agent is one way to control viscosity.

The composition may be applied entirely to the wet pressed mat before drying to form the final mineral fiberboard. Before pressing it may be so applied as to be present throughout the wet mat, with some loss on pressing. After pressing it may be more limited to a wet face. It may all be applied to the back of the finished board after drying. It may be applied one part to the wet mat in process and the remaining part to the dry board.

For example, excellent results in minimizing deforma tion are obtained, using a thickened aqueous composition containing from 35% to content of sodium aluminate, partly in solution.

For a given character of tile the usage of sodium aluminate in pounds per M sq. ft. will vary even for a definite degree of resistance, due to the manner in which it is applied, and due to its distribution in and on the mat.

.The density of the tile also alters the effective quantity.

For example, when applied to a given dry board having a thickness of %-inch and a density of 20 pounds per cu. 11., a usage of 20 pounds is adequate, but applied to the wet mat to be dried to form said board, the usage may vary from 7 to 33 pounds. For convenience, in certain manufacturing operations, it is applied in two stages, for example at the rate of 7 pounds to the wet pressed mat, which is then dried, then at the rate of 15 to 20 pounds and again dried.

A tile meeting the American Society of Testing Materials Test E119-55 is made from the composition in Table II, having a density of 20 pounds per cu. ft., and a thickness in the range from /2 to %-inch. One face of the wet pressed mat to be dried is treated with the composition of Table IV to apply 15 pounds of sodium aluminate per M sq. ft. Then, the mat is dried and to the same face when dry is applied the same composition in quantity to apply 10 pounds of sodium aluminate per M sq. ft. Then, the wet treated face is dried, by passing through an oven or under radiant lamps. The applied composition more easily penetrates the wet mat, so the first application carries the agent slightly inward from the surface and the second application confines it largely over the surface.

Table IV Parts by weight Sodium aluminate 450 Water 550 Methyl cellulose 8 FIG. 5 shows a tile 31 having fibers at its back surface coated with sodium aluminate as indicated at 32, and

fibers adjacent said surface inwardly therefrom, likewise A control tile of 18 pounds per cu. ft., was formed in the conventional manner. A test piece thereof 3 x 8 inches was exposed to a flame at 2000 F. on test supports, and it sagged and dropped in 4 to 5 minutes.

The same furnish was used to make a like tile with the addition of equal molar amounts of zinc chloride and of caustic soda, as follows:

Parts Zince chloride 6.4

Caustic soda 1.85

Flocculating agent 0.032

Tested in the same manner as the control tile, the test tile remained in place for minutes with a maximum deflection of 9 /2 mm.

Sodium zincate is effective when used like sodium aluminate, as described above. Usage of 10 to pounds of sodium zincate on the back of a tile, decreased the sag in a laboratory test in 15 minutes from 12 to 13 mm. for a control tile to 7.5 to 9 mm., for the treated tile.

In the formula of Table V, glass fibers have been substituted with results not quite as good as with slag wool tile. The difference is not explained, possibly resulting from the differences in diameter and length of fiber. The following Table VI shows the comparative times of failure in a laboratory fire-test, with different chemical means in the furnish.

Table VI Glass Fiber Comparable Sag, Chemical Means Usage Failure in Time For mm.

Minutes Slag W001 Control 4. 5 7 Zinc Chloride 4 6. 2 15 12 Zinc Chloride 4 Caustic Soda.. 0.8 10. 75 2 15 4. 5 F100. Agent... 0.02

l Expressed as parts per 100 parts of total fiber. 2 Time not exact, as test stopped after 15 minutes.

The invention is not limited to mineral fiberboard made by draining an aqueous slurry. It may be practiced in air-laying felts to be compressed to tile-density. The dry fibers are discharged into a gravity settling chamber in any well-known manner, and the binder and chemical means are discharged or sprayed into the falling fibers.

A mixture of 95 parts of slag wool, and 5 parts of sulfiite fibers is discharged for gravity felting. Into the falling fibers is sprayed an aqueous cooked starch dispersion to provide 8 parts of starch to the 100 parts of fiber. The moist felt is compressed for drying to a board of 22.3 pounds per cu. ft. This provides a basic formula for a control tile X.

The same formula was used with the addition of 4 parts of zinc chloride and 0.8 part of caustic soda, sprayed into the falling fibers. The dried pressed mat at 23 pounds per cu. ft. provides tile Y.

Tile Z was formed by adding to the control formula 4 parts of sodium aluminate, and compressing to form a board of 30.2 pounds per cu. ft.

Table VII gives the failure time in a laboratory firetest.

8 Table Vll Tile Minutes Y 9.25. Z Sagged 10.25 mm. in

15 minutes.

From the foregoing it will be readily apparent to those skilled in the art how any of the chemical means named, and others suggested thereby, may be used, either in the furnish, or on the tile, when appropriate for the character of the mineral fiber.

Reference is made to a divisional application directed to the subject matter of the ceiling, Serial No. 442,409, filed March 24, 1965.

We claim:

1. Flame-resistant mineral fiber tile comprising an integral fiber felt having sodium aluminate on mineral fibers at a face thereof.

2. Flame-resistant mineral fiber tile comprising an integral fiber felt having sodium aluminate on mineral fibers at a face thereof and on mineral fibers adjacent said face inwardly therefrom.

'3. Flame-resistant mineral fiber tile comprising an integral fiber felt having sodium aluminate on mineral fibers throughout the body thereof.

4. Flame-resistant mineral fiber tile comprising an integral fiber felt having sodium aluminate on mineral fibers including fibers at and adjacent the back of the tile, which sodium aluminate at red heat provides refractory coating on said fibers thereby opposing the tendency of the soheated tile to sag.

5. Tile according to claim 4 in which the sodium aluminate is located only at and adjacent the back of the tile.

6. Tile according to claim 4 in which the sodium aluminate is located throughout the body of the tile.

7. Tile according to claim 4 in which throughout the body of the tile is distributed the insoluble reaction product resulting from use of zinc chloride and caustic soda in the the proportion of two moles of zinc chloride and one mole of caustic soda.

8. Tile according to claim 4 having zinc oxychloride throughout the body of the tile and sodium aluminate at and adjacent the fibers at the back of the tile.

9. Flame-resistant mineral fiber tile comprising an integral fiber tile having chemical means for forming a refractory coating on mineral fibers, said means consisting of sodium aluminate located at a face layer of the tile.

10. A tile according to claim 9 in which the said face is the back of the tile in the position in which it is to be mounted in a ceiling.

11. Flame-resistant mineral fiber tile comprising an integral fiber tile having chemical means for forming a refractory coating on mineral fibers, said means consisting of sodium aluminate located throughout the tile.

12. Flame-resistant mineral fiber tile comprising an integral fiber tile having chemical means for forming a refractory coating on mineral fibers, said means consisting of zinc oxychloride located throughout the tile and of sodium aluminate at a face of the tile.

13. A tile according to claim 12 in which said face is the back of the tile in the position in which it is to be mounted in a ceiling.

References Cited by the Examiner UNITED STATES PATENTS 1,224,145 5/1917 Craig 117-138 XR 1,224,204 5/1917 Perkin 117136 1,225,414 5/1917 Craig 117138 1,397,858 11/1921 Craig 117-136 1,444,051 2/1923 Allison 10615 (Other references on following page) 9 W UNITED STATES PATENTS 2,909,446 10/1959 Redfarn et a1. 117-138 5 32 B 1 2 159 2,944,930 7/1960 Bush et a1. 162159 13 222}, 117 126 2,949,385 8/1960 Malowan 6161 117 -13s 2/1938 Becher 117126 5 FOREIGN PATENTS 24328 23? il 165,114 1955 Australia. 12/1941 Heritag; 276,057 1951 Switzerland. 12/1941 Hal'stead 1171 26 ILLIA D MARTIN P. E

9/1952 Becher 162-159 W M 9 1954 McGarvey 1 2 15 10 W. D. MUSHAKE, JACOB L. NACKENOFF, 8/1959 Shannon 61:31. 117-139 XR Exammers- 

1. FLAME-RESISTANT MINERAL FIBER TILE COMPRISING AN INTEGRAL FIBER FELT HAVING SODIUM ALUMINATE ON MINERAL FIBERS AT A FACE THEREOF. 